ENH: Support exporting/importing of AppBundle targets.

- Imported bundles have the MACOSX_BUNDLE property set
  - Added cmTarget::IsAppBundleOnApple method to simplify checks
  - Document BUNDLE keyword in INSTALL command
  - Updated IMPORTED_LOCATION property documentation for bundles
  - Updated ExportImport test to test bundles

Source/cmExportInstallFileGenerator.cxx

@@ -160,8 +160,8 @@ cmExportInstallFileGenerator
                                     te->RuntimeGenerator, properties);
     this->SetImportLocationProperty(config, suffix,
                                     te->FrameworkGenerator, properties);
-
-    // TODO: Bundles?
+    this->SetImportLocationProperty(config, suffix,
+                                    te->BundleGenerator, properties);
 
     // If any file location was set for the target add it to the
     // import file.
@@ -227,12 +227,17 @@ cmExportInstallFileGenerator
   std::string fname = itgen->GetInstallFilename(config);
   value += fname;
 
-  // Fix name for frameworks.
+  // Fix name for frameworks and bundles.
   if(itgen->GetTarget()->IsFrameworkOnApple())
     {
     value += ".framework/";
     value += fname;
     }
+  else if(itgen->GetTarget()->IsAppBundleOnApple())
+    {
+    value += ".app/Contents/MacOS/";
+    value += fname;
+    }
 
   // Store the property.
   properties[prop] = value;